Second order Class A log domain all pass filter design employing lossy integrators

In this study, a new Class A second order log domain all pass filter is designed by using lossy integrators. An all pass filter has unity gain at all frequencies. It also shifts phase at desired value at the given frequency of the input signal. The proposed filter circuit design is based on Kerwin-Huelsman-Newcomb (KHN) block diagram by using lossy integrators. The circuit is synthesized by using state space synthesis method and the translinear principle. The natural frequency f
₀
of the circuit is electronically tunable by varying amplitudes of the current sources. PSpice simulation results are given to verify the theoretical analysis. The simulations are performed with both ideal transistor models and AT&T CBIC-R type real transistor models.